This invention relates to an apparatus and process for removing film-like contamination from the surface of an electrostatic imaging member. The invention is particularly adapted for use in a xerographic reproducing machine.
In some xerographic reproducing machines film type contamination on the surface of the photoconductive plate has been found to cause deletions in the image on the copy sheet. These deletions are believed to occur due to lateral surface conduction in the contaminant film which has the effect of discharging portions of the electrostatic image on the photoconductive plate. Those portions of the image which have been so discharged then show up as deletions in the resulting copy sheet. The film material is believed to be made up principally of organic components including toner degradation products and other species as well as one or more inorganic elements or compounds. These film type contaminants are believed to be derived from environmental sources, both internal and external of the machine. Contamination films of this type have been found to be resistant to conventional xerographic plate cleaning procedures such as the use of a resilient cleaning blade.
Various procedures for removing residual toner particles and other types of particulate components from the surface of an electrostatic imaging member are known, as for example, the use of resilient blades, brushes, webs, or the like. Numerous systems have been proposed wherein more than one cleaning element is provided in order to have redundancy in the cleaning system. Thereby, if the first cleaning element fails or incompletely removes toner particles, the second cleaning element will remove those remaining particles. For example, U.S. Pat. No. 3,552,850, granted Jan. 5, 1971, to Royka et al. discloses the use of multiple cleaning blades. In U.S. Pat. No. 3,795,025, the use of multiple brushes as a cleaning system is disclosed. In German Offenlegungsschrift, 2,111,509, laid open for public inspection Sept. 23, 1971, there is disclosed a redundant cleaning system comprising a blade which removes the predominant portion of any residual toner particles and a cleaning roller following the blade for removing any remaining particles. The surface of the roller is covered with a coating of woven or knitted cloth, suede or the like. It is alleged that the wiper and the roller operate according to different principles so that their disadvantages are balanced and complete cleaning can be achieved. It is not known whether these redundant cleaning systems would be effective to remove contaminant films of the type described above.
In addition to the foregoing prior art, there is provided in U.S. Pat. No. 3,664,300, granted May 23, 1972, to Joseph, a system for applying lubricants to the surface of an electrostatic imaging member. In accordance with one embodiment thereof, a bar brush applicator is employed. The lubricant applicator may be located in the imaging cycle following a cleaning system or as described and shown it may act in a dual fashion as the basic cleaning system.